JP2007266690A - Current drive circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current drive circuit wherein the settling with respect to a change in an oscillation frequency of a current controlled oscillator is sufficiently small and the temperature dependence of the oscillation frequency is sufficiently low while achieving a high filtering effect to a noise gain at a high frequency band. <P>SOLUTION: A conventional current drive circuit for supplying a current to the current controlled oscillator (e.g. a YIG oscillator) whose oscillation frequency is changed depending on the received current is improved. The current drive circuit disclosed herein is characterized in to include: a capacitor provided in parallel with the YIG oscillator; a resistor provided in parallel with the YIG oscillator; a current output section respectively connected to the YIG oscillator, the capacitor, and the resistor and supplying a current to them in response to a voltage received by the current output section; a temperature detection means for detecting a temperature of the YIG oscillator; and a gain variable means for increasing/decreasing the voltage applied to the current output section on the basis of the temperature detected by the temperature detection means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a measuring instrument that generates a broadband high-frequency signal (for example, several [kHz] to several tens [GHz]), a measuring instrument that measures and analyzes a broadband high-frequency signal (for example, a demodulator for a modulation signal, a spectrum). More specifically, the current drive circuit for controlling the oscillation frequency of a current-controlled oscillator (eg, YIG oscillator) used in an analyzer or the like, and more specifically, the oscillation frequency of the YIG oscillator while achieving a high filtering effect on noise gain in a high frequency range. The present invention relates to a current drive circuit in which the settling is sufficiently small with respect to the change in the frequency and the temperature dependence of the oscillation frequency is sufficiently low.

  It is necessary to use an oscillator having good frequency characteristics (for example, stability to temperature, low noise, etc.) for a measuring instrument that generates a wide-band high-frequency signal, a measuring instrument that measures and analyzes a wide-band high-frequency signal, and the like. As such an oscillator, for example, a YIG (Yttrium-Iron-Garnet) oscillator (hereinafter, YIG oscillator is abbreviated as YTO (YIG Tuned Oscillator)) is used. In YTO, the magnetic resonance of YIG is applied to control the amount of current flowing in the main coil of YTO by a current drive circuit, thereby controlling the oscillation frequency of the output signal (see, for example, Patent Documents 1 and 2).

FIG. 4 is a diagram showing a configuration of a conventional current drive circuit.
In FIG. 4, a YTO 10, a power transistor 11, and a resistor 12 are connected in series, and a predetermined voltage Vcc is applied. The bypass capacitor 13 is provided in parallel with the YTO 10. The collector side of the power transistor 11 is connected to the YTO 10 and the bypass capacitor 13, and the emitter side is connected to one end of the resistor 12. The other end of the resistor 12 is connected to a common potential. Here, the transistor 11 and the resistor 12 constitute a current output unit.

  The coil 10a is a main coil of the YTO 10, and the resistor 10b is an equivalent series resistance of the coil 10a. The YTO 10 includes a YIG, a magnet for exciting the YIG, a yoke around which the coil 10a is wound to form a magnetic path, etc., but these are not shown.

The operation of such a circuit will be described.
A control voltage V <b> 1 is input to the base of the transistor 11 from a control voltage generator (not shown). As a result, a base-emitter voltage (hereinafter referred to as Vbe) of the transistor 11 and a control current I1 according to the resistor 12 are generated. That is, the resistor 12 can be regarded as an element for current-voltage conversion.

  The control current I1 is divided into a drive current I2 flowing through the YTO 10 and a bypass current I3 flowing through the capacitor 13 in accordance with the impedance ratio between the main coil 10a of the YTO 10 and the bypass capacitor 13. Furthermore, the frequency of the output signal output from the YTO 10 is controlled by the amount of current (current value) of the drive current I2.

  In addition, current noise included in the control current I1 also flows to the drive current I2 and frequency-modulates the output signal of the YTO 10, but by providing the capacitor 13, the capacitor 13 suppresses current noise and prevents frequency modulation. Yes. Thereby, it can prevent that the signal purity of an output signal falls.

  FIG. 5 is a diagram showing another configuration of a conventional current drive circuit. Here, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 5, a damping resistor 14 is provided in parallel with the YTO 10 and the capacitor 13. A predetermined voltage Vcc is applied to one end of the damping resistor 14 and the other end is connected to the collector side of the transistor 11.

The operation of such a circuit will be described.
The control current I1 is divided into a drive current I2, a bypass current I3, and a current I4 flowing through the resistor 14 corresponding to the impedance ratio of the main coil 10a of the YTO 10, the bypass capacitor 13, and the resistor 14. Other operations are the same as those of the apparatus shown in FIG.

  FIG. 6 is a diagram showing another configuration of a conventional current drive circuit. Here, the same components as those shown in FIG. In FIG. 6, a damping circuit 15 is provided instead of the capacitor 13. In the damping circuit 15, a capacitor 15a and a resistor 15b are connected in series.

The operation of such a circuit will be described.
The control current I1 is divided into a drive current I2 and a current I5 flowing through the damping circuit 15 corresponding to the impedance ratio between the main coil 10a of the YTO 10 and the damping circuit 15. Other operations are the same as those of the apparatus shown in FIG.

JP 2001-141765 A JP 2002-151912 A

  In the circuit shown in FIG. 4, the resonance frequency is determined by the inductance value of the main coil 10 a and the capacitance of the bypass capacitor 13. The noise gain above the resonance frequency can be attenuated by −40 [dB / dec] by selecting the capacitance of the capacitor 13. That is, it is possible to obtain a filtering effect for noise exceeding the band necessary for settling.

  However, this resonance is current resonance, and in general, the resistance value of the equivalent series resistance 10b of the main coil 10a is very small, about several [Ω]. For this reason, it takes a long time for the once-resonated current to converge. For example, when the control voltage V1 is changed stepwise, there is a problem that settling of the drive current I2 according to the resonance frequency occurs.

  Here, FIG. 7 is a diagram showing the frequency characteristics of noise of the circuits shown in FIGS. The horizontal axis is the noise frequency, and the vertical axis is the noise gain. 7A to 7C show the frequency characteristics of the circuits shown in FIGS. 4 to 6. In FIGS. 7B and 7C, the frequency characteristics of the circuits shown in FIG. It is shown by.

  In the circuit shown in FIG. 5, a damping resistor 14 is provided to improve the current resonance shown in FIG. However, by providing the damping resistor 14, a shunt current (current I2 and current I4) of the control current I1 in a DC state that did not exist in the circuit shown in FIG. 4 is generated.

  In general, the equivalent series resistance 10b of the main coil 10a has temperature dependence due to a change in conductivity temperature of a metal used for the conductive wire of the coil 10a. For this reason, when the temperature of the YTO 10 changes, the resistance value of the equivalent series resistance 10b also changes, and the shunt ratio of the currents I2 and I4 also has temperature dependence. Therefore, the drive current I2 also has a temperature dependency, and there is a problem that the frequency dependency of the output signal frequency of the YTO 10 also occurs.

  Here, FIG. 8 is a diagram showing the characteristics of the change in the frequency of the output signal due to the change in the resistance value of the equivalent series resistance 10b generated in the circuit shown in FIG. As shown in FIG. 8, the resistance value of the equivalent series resistance 10 b increases as the temperature of the YTO 10 increases, and as a result, the oscillation frequency decreases.

  In the circuit shown in FIG. 6, the damping circuit 15 is used to improve the shunting of the control current I1 in the DC state shown in FIG. 5, and the influence of the temperature dependence of the equivalent series resistance 10b is suppressed. However, the resistor 15b in the damping circuit 15 functions to cancel the filtering effect of the capacitor 15a (because the capacitor 15a functions as a resistor as the noise frequency of the current noise increases), as shown in FIG. In addition, there is a problem that the noise gain in the high band is attenuated only when it is about −20 [dB / dec], and the noise filtering effect is lowered.

  Accordingly, an object of the present invention is to achieve a high filtering effect on a noise gain in a high frequency (above the resonance frequency), settling is sufficiently small with respect to a change in the oscillation frequency of the YTO 10, and the temperature dependency of the oscillation frequency is also sufficient. It is to realize a low current drive circuit.

The invention described in claim 1
In a current drive circuit that supplies current to a current-controlled oscillator whose oscillation frequency changes according to the amount of current,
A capacitor provided in parallel with the current-controlled oscillator;
A resistor provided in parallel with the current-controlled oscillator;
A current output unit that is connected to each of the current-controlled oscillator, the capacitor, and the resistor, and causes a current amount to flow according to an applied voltage;
Temperature detecting means for detecting the temperature of the current controlled oscillator;
Gain varying means for increasing or decreasing the voltage to the current output unit based on the temperature detected by the temperature detecting means is provided.
The invention according to claim 2 is the invention according to claim 1,
The current output unit is characterized in that a transistor and a resistor are connected in series, and a voltage from a gain varying means is applied to the base of the transistor.
The invention according to claim 3 is the invention according to claim 1 or 2,
The temperature detection means is a resistance whose resistance value changes with temperature,
The gain variable means is an operational amplifier using the resistor as a feedback resistor.
The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The current controlled oscillator is a YIG oscillator.

The present invention has the following effects.
According to the first to fourth aspects, the capacitor and the resistor are provided in parallel with the current control type oscillator, and the gain variable means changes the gain according to the temperature of the temperature detection means for detecting the environmental temperature of the current control type oscillator. Since the voltage to the current output unit is increased or decreased, the settling is sufficiently small even if the voltage for controlling the oscillation frequency is changed stepwise while securing the characteristics of the noise gain filtering effect at high frequencies. Even if the environmental temperature of the controlled oscillator changes, it is possible to obtain characteristics in which the temperature dependence of the oscillation frequency is sufficiently reduced.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of the present invention. Here, the same components as those shown in FIG. In FIG. 1, temperature detection means 20 and gain variable means 21 are newly provided.

  The temperature detection means 20 detects the temperature in the vicinity of the coil 10a of the YTO 10. For example, the YTO 10 is generally sold in a predetermined case. Since the temperature in the case of the YTO 10 can be regarded as constant, the case temperature is detected by bringing the temperature detection means 20 into contact with the case. Of course, the temperature detecting means 20 may be provided near the coil 10a in the case. In short, it is only necessary to detect a temperature change of the coil 10a.

  The gain variable means 21 receives a control voltage V1 from a control voltage generator (not shown) and changes the gain based on the temperature detected by the temperature detection means 20, that is, the amplitude (voltage) of the control voltage V1. Value) is increased or decreased and output to the base of the transistor 11.

The operation of such a circuit will be described.
First, the operation when the case temperature is constant will be described.
The temperature detection means 20 detects the case temperature of the YTO 10 and outputs the detected temperature to the gain variable means 21. Then, the gain variable means 21 adjusts the gain based on the temperature, increases or decreases the control voltage V1 from the control voltage generator (not shown), and converts the control voltage V1 ′ whose voltage value is adjusted into the transistor 11 is applied to the base. Thereby, the control current I1 according to the voltage Vbe of the transistor 11 and the resistor 12 is generated.

  The control current (collector current of the transistor 11) I1 corresponds to the impedance ratio of the main coil 10a, the bypass capacitor 13 and the damping resistor 14 of the YTO 10, and the drive current I2 flowing in the YTO 10 and the bypass current flowing in the capacitor 13. The current is divided into I3 and current I4 flowing through the resistor 14. Further, the frequency of the output signal output from the YTO 10 is controlled by the drive current I2. For example, when the frequency of the output signal is increased, the control voltage V1 is increased from a control voltage generator (not shown), and when the frequency is decreased, the control voltage V1 is decreased.

Next, the operation when the case temperature changes will be described.
The temperature detection means 20 detects the changed case temperature and outputs the detected temperature to the gain variable means 21. Then, the gain varying means 21 adjusts the gain so that the drive current I2 is constant before and after the change, and outputs the voltage V1 ′ obtained by adjusting the control voltage V1 to the transistor 11. That is, in the DC state (the state in which the control voltage V1 does not change), the control current I1 is divided into the current I2 and the current I4. However, since the resistance value of the resistor 14 is constant, the resistance value of the equivalent series resistor 10b changes. Based on this, the drive current I2 changes. Therefore, from the relationship between the temperature and the resistance value of the equivalent series resistance 10b, the gain variable means 21 adjusts the gain with respect to the voltage V1 so that the drive current I2 is constant without depending on the temperature.

  For example, at 25 ° C., control current I1 = 300 [mA], equivalent series resistance 10b = 10 [Ω], and damping resistance 14 = 100 [Ω]. The drive current I2 in this state is about 273 [mA] (= 300 [mA] × 100 [Ω] / (10 [Ω] +100 [Ω])), and the current I4 is about 27 [mA] (= 300 [mA] -273 [mA]).

  Next, the case where the environmental temperature of the YTO 10 is changed from 25 ° C. to 75 ° C. and the resistance value of the equivalent series resistance 10b is changed from 10 [Ω] to 12 [Ω] will be described.

  In the circuit shown in FIG. 5, when the resistance value of the equivalent series resistance 10b changes (from 10 [Ω] to 12 [Ω]), the drive current I2 is about 268 [mA] (= 300 [mA] × 100 [ Ω] / (12 [Ω] +100 [Ω])), and the current I4 increases to about 32 [mA] (300 [mA] -268 [mA]). As described above, as the temperature of the YTO 10 increases, the frequency of the output signal of the YTO 10 decreases.

  On the other hand, in the circuit shown in FIG. 1 of the present invention, the temperature detection means 20 detects the case temperature and outputs the detected temperature to the gain variable means 21. Then, the gain variable means 21 adjusts the gain based on the detected temperature to increase the control voltage V1. That is, the gain varying means 21 increases the gain of the voltage V1 by 1.8 [%] (= (112 [Ω] −110 [Ω]) / 110 [Ω] × 100). As a result, about 273 [mA] (= 300 [mA] × 100 [Ω] / (12 [Ω] +100 [Ω]) × (1 + 0.018)), which is the same as the temperature of 25 ° C., flows through the drive current I2. Therefore, even if the temperature changes from 25 ° C. to 75 ° C., the drive current I 2 is constant, and the frequency of the output signal of the YTO 10 is also kept constant.

  Here, FIG. 2 is a diagram showing the frequency characteristics of the noise of the circuit shown in FIG. 1 and the characteristics of the change in the frequency of the output signal due to the change in the resistance value of the equivalent series resistance 10b. Since the capacitor 13 and the resistor 14 are provided in parallel with the YTO 10 and shunt the control current I1, a high frequency noise gain characteristic (for example, −40 [dB / dec]) is achieved, and the oscillation frequency control voltage Even if is changed stepwise, the settling is sufficiently small (see FIG. 2A). Further, even if the resistance value of the equivalent series resistance 10b changes, the frequency of the output signal of the YTO 10 is kept constant (see FIG. 2B).

  Thus, the capacitor 13 and the resistor 14 are provided in parallel with the YTO 10, and the gain variable means 21 changes the gain according to the temperature of the temperature detection means 20 that detects the environmental temperature of the YTO 10, and increases or decreases the control voltage V1. Therefore, (a) while ensuring the characteristics of high-frequency noise gain (for example, −40 [dB / dec]), (b) sufficient settling even if the control voltage of the oscillation frequency is changed stepwise (C) Even if the environmental temperature of the YTO changes, it is possible to obtain characteristics in which the temperature dependence of the oscillation frequency is sufficiently reduced.

  FIG. 3 is a block diagram showing a specific embodiment of the apparatus shown in FIG. Here, the same components as those in FIG. A thin film linear resistor 20a is used for the temperature detecting means 20, and is attached to the case of the YTO 10. The thin film linear resistor 20a has a positive temperature coefficient, the resistance value increases as the temperature increases, and the resistance value decreases as the temperature decreases. The characteristics of temperature and resistance value have linearity. One end of the thin film linear resistor 20 a is connected between the transistor 11 and the resistor 12.

  As the variable gain means 21, an operational amplifier 21a and a resistor 21b are used. The control voltage V1 is input to the non-inverting input terminal of the operational amplifier 21a, and the other end of the thin film linear resistor 20b is connected to the inverting input terminal. The inverting input terminal is connected to the common potential via the resistor 21b. Further, the output terminal of the operational amplifier 21 a is connected to the base of the transistor 11. That is, the operational amplifier 21a and the resistors 20a and 21b form a non-inverting amplifier circuit.

The operation of such a circuit will be described.
When the temperature rises, the resistance value of the thin film linear resistor 20 increases and the gain of the operational amplifier 21a also increases. Then, the voltage V1 ′ applied to the transistor 11 also increases and the control current I1 also increases. As a result, even when the resistance value of the equivalent series resistance 10b increases, the drive current I2 is kept constant, and the frequency of the output signal of the YTO 10 is also kept constant without depending on the temperature. Conversely, when the temperature decreases, the resistance value of the thin film linear resistor 20 decreases, the gain of the operational amplifier 21a also decreases, the voltage V1 ′ decreases, and the control current I1 also decreases. As a result, even if the resistance value of the equivalent series resistance 10b decreases, the drive current I2 is kept constant, and the frequency of the output signal of the YTO 10 is also kept constant without depending on the temperature. Of course, the resistance value of the resistor 21b, the resistance value of the thin film linear resistor 20a, and the change rate are selected in advance so as to compensate for the temperature dependence of the equivalent series resistance 10b.

The present invention is not limited to this, and may be as shown below.
Although the example which comprises the transistor 11 and the resistor 12 is shown as the current output unit, any device may be used as long as the amount of current (current value) increases or decreases in proportion to the applied voltage.

  Although the configuration using the thin film linear resistor 20a having a positive temperature coefficient as the temperature detecting means 20 is shown, a resistor having a negative temperature coefficient may be used. In this case, the operational amplifier 21a may be an inverting amplifier circuit.

  Although the configuration in which the thin film linear resistor 20a whose resistance value changes linearly with respect to the temperature is used as the temperature detection unit 20, a resistor whose resistance value changes nonlinearly may be used.

  An example of a configuration in which the gain is adjusted using the operational amplifier 21a is shown as the gain variable unit 21. However, any device may be used as long as the gain can be adjusted based on the temperature.

  Although an example of controlling the frequency of the output signal of the YTO 10 has been given, this circuit is not limited to the YTO 10 and may be used for a current-controlled oscillator whose oscillation frequency changes according to the amount of current.

It is the block diagram which showed one Example of this invention. It is the figure which showed the frequency characteristic of the noise of the circuit shown in FIG. 1, and the characteristic of the change of the frequency of an output signal by the change of the resistance value of an equivalent series resistance. It is the block diagram which showed an example of the temperature detection means of the apparatus shown in FIG. 1, and a gain variable means. It is the figure which showed the structure of the conventional current drive circuit. It is the figure which showed the other structure of the conventional current drive circuit. It is the figure which showed the other structure of the conventional current drive circuit. It is the figure which showed the frequency characteristic of the noise of the circuit shown in FIGS. It is the figure which showed the characteristic of the change of the frequency of an output signal by the change of the resistance value of the equivalent series resistance in the circuit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 YIG oscillator 10a Main coil 10b Equivalent series resistance of main coil 11 Power transistor 12, 14, 21b Resistance 13 Capacitor 20 Temperature detection means 20a Thin film linear resistance 21 Gain variable means 21a Operational amplifier

Claims (4)

In a current drive circuit that supplies current to a current-controlled oscillator whose oscillation frequency changes according to the amount of current,
A capacitor provided in parallel with the current-controlled oscillator;
A resistor provided in parallel with the current-controlled oscillator;
A current output unit that is connected to each of the current-controlled oscillator, the capacitor, and the resistor, and causes a current amount to flow according to an applied voltage;
Temperature detecting means for detecting the temperature of the current controlled oscillator;
A current drive circuit comprising gain variable means for increasing or decreasing the voltage to the current output unit based on the temperature detected by the temperature detection means.   2. The current drive circuit according to claim 1, wherein the current output unit includes a transistor and a resistor connected in series, and a voltage from the gain varying means is applied to a base of the transistor. The temperature detection means is a resistance whose resistance value changes with temperature,
3. The current drive circuit according to claim 1, wherein the gain variable means is an operational amplifier using the resistor as a feedback resistor. The current drive circuit according to claim 1, wherein the current control type oscillator is a YIG oscillator.

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